Quick-make and quick-break switch

ABSTRACT

This invention relates, generally, to quick-make and quick-break types of switches and, more particularly to an improved quickmake and quick-break type of switch, which may be readily mounted on transformer installations and operated with facility for sectionalizing cables in the distribution system, and as a loadbreak switch at the transformer itself.

United States Patent Merrill G. Leonard [72] lnventor Fowler, Ohio [21]ApplNo 657,114 [22] Filed .1u1y31.1967 [45] Patented June 29, 1971 73]Assignee Westinghouse Electric Corporation Pittsburgh, Pa.

[54] QUICK-MAKE AND QUICK-BREAK SWITCH 19 Claims, 28 Drawing Figs. [52]U.S. Cl 200/67, 200/67, 174/151, 336/137, ZOO/166, 200/168, 200/70 [51]Int. Cl 1101b 13/28 [50] Field of Search 200/67 PK, 70, 67,166 E, 1668,168 G, 170 A, 67 PK, 67 B, 167 R; 174/151 [56] References Cited UNITEDSTATES PATENTS 3,194,909 7/1965 Epstein 200/78 X 3,212,346 10/1965Bachman.. 200/67 A 648,555 5/1900 Ely. 200/70 1,499,139 6/1924 Arnold etal ..200/67 PKS (UX) 1,517,638 12/1924 Kellner .200/67 PKS (UX)2,534,007 12/1950 Dietrich ..200/67 PKS (UX) 2,918,541 12/1959 Waite....200/166E (UX) 3,027,440 3/1962 Daly ....200/166 E (UX) 3,101,3878/1963 Mihran 171/151X Primary Examiner David Smith, Jr Attorneys-A. T.Stratton, C. L. McHale and W. R. Crout ABSTRACT: This invention relates,generally, to quick-make and quick-break types of switches and, moreparticularly to an improved quick-make and quick-break type of switch,which may be readily mounted on transformer installations and operatedwith facility for sectionalizing cables in the distribution system, andas a load-break switch at the transformer itself.

PATENTEB M29 s7! SHEET 1 OF 8 07////////// 0I//// I I I FlG.l.

INVENTOR Merrill G. Leonard WITNESSES W ATTORNEY PATENYEU Juuzs an SHEEY2 OF 8 PATENTED JUN29|97| 3590.183

SHEET u or 8 FIGS.

PATENTEU JUN29l97| 590, 1 83 sum 5 or '8 PATENIED M29 m sum 6 0F 8 (LowVOLTAGE COMPARTMENT |5KV 1 1m: (LOOP) Low- VOLTAGE COMPARTMENTPATENTEDJUN29|97l 3590.183

' SHEET 7 0F 8 fl llllff/l/ 1 QUICK-MAKE AND QUIGK-BREAK SWITI-I Ageneral object of the present invention is to provide an improvedquick-make and quick-break type of switch, which will not only result infast opening and closing movement, but, additionally, will provide apositive opening and closing action even if the contacts haveconsiderable frictional engagement.

Another object of the present invention is the provision of an improvedquick-make and quick-break type of switch, which may be readily adaptedfor a wide variety of switching connections.

Another object of the present invention is the provision ofa quick-makeand quick-break type of switch, which may be operated easily byservicemen in connection with submersible types of transformerinstallations.

Another object of the present invention is the provision ofa quick-makeand quick-break type of switch in which the do tent action on the driven.crank arm may be positively controlled without hampering the actuatingmotion of the switch.

Still a further object of the present invention is the provision .of animproved quick-make and quick-break type of switch adaptable for volumemanufacture, and composed of relatively few easily manufactured andreadily assembled items.

Still a further object of the present invention is the provision of animproved mounting construction for a quick-make and quick-break type ofswitch which will accommodate a wide variety of misalignment conditionsin the assembly operations by relatively unskilled workmen.

Another object of the present invention is the provision ofa quick-breakand'quick-make type of switch having aligned rotating driver and drivencrank arms, in which kickers," or actuating members, are engaged by thedriving crank arm to insure positive opening and closing motion of thedriven crank arm to break any possible welding, or frictional conditionsat the separable contact members.

Another object of the invention is to provide a quick-make andquick-break type of switch mechanism having positive actuators orkickers" to overcome frictional or slight welding conditions at theseparable contact structure, in which a correct indication of switchposition is provided even if, due to excessive welding, the actuatorsbecome incapable of operation.

In accordance with a preferred embodiment of the invention, a manuallyoperated driving crank arm, carrying one end of an overcenter spring, isprovided having the other end of the overcenter spring connected to thefree end ofa driven, or follower crank arm, which actuates the movablecontact structure. A moving portion of the driving crank arm engages atthe end extremities of its opening and closing motion a pair ofpivotally mounted kickers, or actuators, which positively engage thespring support member secured to the free end of the driven crank arm,and supporting the end of the overcenter spring. As a result, movementof the overcenter spring by the driving crank arm will effect snapopening and closing movement of the driven crank arm, and henceoperation of the contact structure, with positive operating movement ofthe contact structure assured at the end of the opening and closingmovements ofthe driving crank arm.

According to another embodiment of the invention, the spring-support pinon the driven crank arm rides in a slot, or cam surface cutout of astationary frame member to thereby permit more variety in detent actionthan is possible with a fixed bearing.

Preferably, each of the aforesaid embodiments is supported in a novelmanner capable of accommodating misalignment of the moving contactassembly by having a bearing sleeve guiding the rotative motion of thedriving crank arm and secured to the switch frame, with the said sleevebearing having a pilot action in a stationary guide-sleeve bearingfixedly secured to the tank cover, or sidewall ofthe adjacent tankstructure,

Further objects will readily become apparent upon reading the followingspecification, taken in conjunction with the drawings, in which:

FIG. I is a sectional perspective view of a submersible-type transformendesignated Type SPB" manufactured by the Westinghouse ElectricCorporation and developed for underground distribution systems;

FIG. 2 is a fragmentary view looking down into the underground vaultshowing the upper end of the submersibletype transformer of FIG. l;

FIG 3 is a diagrammatic view ofa typical loop-type distribution systemto indicate the necessity for switching at the individual transformerunits for house and str'eetlighting circuits, and illustrating thelocation of the load-break switches associated with each of the unittransformer-s;

FIG. 4 is a fragmentary perspective view of the load-break switch of thepresent invention mounted in the dome cover of a subway pole basetransformer of the type set forth in FIGS. l and 2, and illustrating theposition of a plurality of contact structures in a closed connectingposition;

FIG. 5 is an enlarged side elevational view of the quickbreak andquick-make type of load-break switch of the present invention, assecured to the tank cover or sidewall of a distribution transformer,thecontact structure being illustrated in the closed-circuit position;

FIG. 6 is an end elevational view of the switch structure of FIG. 5;

FIG. 7 is a top plan view of the switch structure of FIGS 5 and 6, withreference being had to FIG. 4;

FIG. 7A is a fragmentary top plan view of a portion of the switchmechanism in the closed-circuit position;

FIG. 8 is an exploded perspective view of the switch in the closedposition with some portions of the switch omitted for clarity;

FIG. 9 is an enlarged view of two stationary cooperative contact fingersand indicating their relationship with a moving bridging contact blade;

FIGS. l0 and ll illustrate fragmentarily the partially open and fullyopen circuit positions of the separable contact structure;

FIG. 12 is a fragmentary vertical sectional view taken substantiallyalong the line XII-XII of FIG. 7 illustrating the provided supportingand alignment action associated with the upper frame support and drivingcrank arm, together with a sealed construction to the tank cover;

FIGS. 13-16 illustrate variant types of circuit connections,

which may be obtained with the novel switch structure of the presentinvention;

FIG. l7 illustrates a pad-mounted transformer installation utilizinganother embodiment of the switch structure; and il' lustratesdiagrammatically the relationship of the pad; mounted transformerrelevant to a surrounding residential neighborhood;

FIG. 18 illustrates the location of the second embodiment of the switchstructure in the high-voltage compartment of the pad-mounted transformerof FIG. l7;

FIG. l9 illustrates diagrammatically the internal circuit connections ofthe pad-mounted transformer of FiGS. l7 and 18',

FIG. 20 illustrates in vertical section, a second embodiment of theswitch structure of the present invention in which the spring supportmember of the driven, or follower crank arm is positively guided by camaction, the contact structure being il lustrated in the closed-circuitposition and the view being taken along the line XX-XX ofFIG. 21',

FIG. 21 is a top plan view in section of the modified switch structureof FIG. 20, the view being taken substantially along the line XXL-XXIof'FIG. 20;

FIGS. 22-24 illustrate fragmentarily, modified types of cam slot actionas applied to the switch construction of FIG. 20;

FIG. 25 illustrates partially in side elevation, and partially invertical section, a modified type of contact structure, which may beapplied to either of the switch mechanisms of FIG. 5 or FIG. 20, thecontact structure being shown in the closed-circuit position and takenalong the line XXV-XXV of FIG. 26;

FIG. 26 is an inverted plan view in section of the modified typeofcontact structure shown in FIG. 25 taken substantially along the lineXXVI-XXVI of FIG. 25; and,

FIG. 27 is a considerably enlarged view of one of the resilient contactfingers of FIGS. 25 and 26.

FIGS. l-l9 FIRST EMBODIMENT With reference to the drawings, and moreparticularly to FIG. 1 thereof, the reference numeral 1 generallydesignates a submersible-type transformer, of the Type SPB" manufacturedby the Westinghouse Electric Corporation, and developed to provideunderground distribution circuits for residential neighborhoods.Generally, the submersible-type transformer 1 comprises an undergroundvault 2 positioned in an excavation 3 dug out ofthe ground. The vault 2has a flushmounted grate 4 secured thereto at ground level. Withreference to FIGS. 1 and 2, it will be observed that a distributiontransformer 6 is located within the cylindrical housing member or vault2, and, at times, may be completely submerged with water. As well knownby those skilled in the art, the transformer 6 comprises a high-voltagewinding 7 (FIG. I3) and a low-voltage secondary winding 8, which areinductively coupled.

By way of illustration only, and not by way of limitation, thetransformer 6 may have a KVA rating of say, for example, 25 to I67, andmay be designed for systems rated kv., grounded Y" and below. Twohigh-voltage bushings ll, 12 are secured to the upper dome cover [3, andalso three bushings 15l7 are mounted on the cover'l3 being connected tothe secondary winding 8. Preferably plug-in high-voltage connectors,sold under the trade name Elastimold by the ESNA Corporation, anddescribed in U.S. Ruete et al. Pat. No. 3,243,756, are provided forsubmersible applications. The standard Type SPB transformer isinternally connected for a loop feed primary and a 240/I secondary. Thetwo primary bushings ll, l2 are connected internally by a 200 ampere busthat completes the external feeder loop. The line side of the primarywinding 7 is connected to the internal feeder bus, and the other side ofthe primary winding 7 is internally grounded to the transformer tank, asat 14 (FIG. 13).

The secondary winding 8 is internally connected at either end to the twolow-voltage bushings l5, l7. A neutral center tap terminates at theneutral low-voltage bushing l6, and is externally grounded to thetransformer tank. As shown, the neutral terminal l6 has a porcelaininsulator, and is of the v spade type.

Reference may be had to a typical loop distribution system 21, asillustrated in FIG. 3 of the drawings, to illustrate the lo cation of anumber of transformers 6 of the type set forth in FIG. I in relation toa residential neighborhood. It will be noted that the primaryhighvoltage winding 7 may be connected by either of two load-breakswitches 23 to either side "A" or 8" of the loop. This is desirable forsectionalizing cable connections 25-32, and as a load break switch atthe transformer 6.

In the particular application of the quick-break and quickmake switch 23of the present invention, the switch 23 is mounted inside thetransformer tank 9. The switch 23 may be manually operated by anexternally situated operating handle 34, mounted on the dome cover 13 ofthe transformer tank 9. The switch 23 offers the following four switchpositions;

I. Feedthrough, transformer 6 energized.

II. Feed from left side A of loop (FIG. 3), right side B of loop open,transformer 6 energized.

III. Feed from right side B ofloop (FIG. 3), left side of loop open,transformer 6 energized.

IV. Left and right sides and 8" ofloop (FIG. 3) open,

transformer 6 disconnected from loop.

These switching positions enable the operating personnel to quicklyisolate a line fault in a Asystem 21. while still mainaining fullservice. Or, a transformer 6 can be quickly disconccted from the loopfor maintenance or changcout without disrupting the service of theremaining transformers 6 on the loop. This switching flexibility of theswitch 23 enables utilities to minimize outage time during emergencies.

The present invention is particularly concerned with a novel type ofquick-make and quick-break load-break switch 23, which insures positiveactuation despite frictional, or welding conditions at the contacts 35,36, either in the open or closedcircuit positions. FIG. 4 illustratesthe mounting of the switch 23 in the dome cover l3 of the distributiontransformer 6 of FIG. I, and the disposition of the eyelet operatinghandle 34, which effects switch actuation. The operating handle 34 maybe rotated to open" and closed" positions by a switch stick, as wellknown by those skilled in the art.

FIGS. 5,6 and 7 collectively illustrate side, end and top views,respectively, of the switch structure 23 in the closedcircuit position.With particular reference being directed to FIG. 5 and to the sectionalview of FIG. I2, it will be observed that a sealing sleeve 39, with arelatively large O-ring 40 mounted therein, is securely welded in anopening 41 prcvided in the top dome cover l3 of the transformer 6.Extending downwardly axially within a slightly enlarged opening 42,provided by the sealing sleeve 39, is an actuating shaft'44, the lowerend 44a of which is welded to an offstanding driving crank arm, orspring bracket 46, having an outer spring-support portion 47 at the freeextremity thereof. Reference may be had to FIG. 8 in this connection.

It will be observed that the shank portion of the actuating shaft 44extends through a bearing sleeve 49 (FIG. 12), which is welded, as at51, to the upper side of a frame support 7 member 53, which, in turn, isfixedly secured by mounting bolts 55 to a supporting bracket 57 havingan aperture 53 therethrough, and fixedly secured, as by welding at 60,to the sealing sleeve 39. Thus, the sealing function through the tank isprovided by the fixed sleeve 39 having the slightly enlarged bore 42therethrough, the bearing function is provided by the frame 61 of theswitch 23, the concentricity is provided by the pilot action of anupstanding shoulder portion 49a of the bearing sleeve 49, and any slightangular misalignment is permitted by the clearance 42 in the shortsealing sleeve 39 and the design of the O-ring 40.

With reference to FIGS. 5,6 and 8, it will be noted that an overcenterspring 63 has one end 63a thereof secured to the spring support portion47 of the driving operating crank 46, and the other end 63b of theovercenter spring 63 is securely fastened to an upstanding springsupport portion 64 of a driven, or follower crank arm 65, which iswelded to a square operating shaft portion 66. Reference may be had toFIG. 8 in this connection.

The shaft portion 66, secured to the driven crank arm 65, is insertedwithin a rectangular opening 67 provided by a downwardly extendinginsulating square tubular shaft portion 68 so as to effect the rotationthereof, as brought about by rotative driven action of the crank arm 65.

At the lower end of the tubular square insulating shaft 68 is a squareshaft portion 69, which is secured, as by welding, to a rotatablemovable bridging contact 71 having the movable end portions 75, 76thereof making separable contacting en- 'gagement with a pair of spacedcontact finger assemblies 35, 36, the latter being fixedly mounted andmore particularly described hereinafter.

To limit the end positions of the rotative action of the driving crankarm 46, there is provided a pair of downwardly jutting tabs 77, 78,which are bent down from a configured plate portion of the top frame 53,thereby constituting stop, or limiting portions for restricting the endrotative opening and closing motion of the driving is provided arm 46.

In similar manner, to limit the opening and rotative end positions ofthe driven, or follower crank arm 65, there is provided a pair ofupstanding tabular portions 82, 83 bent upwardly from the lower framemember 85 and serving to arrest opening and closing motions of thedriven crank arm 65. As will be obvious, the overcenter spring 63provides a quickmake and quick-break action once its line of actionextends over the centerline 86 (FIG. 10) of the device.

In the event that there is considerable friction between the rotativebridging member 71 and the cooperable spaced stationary finger contactassemblies 35, 36, or should there be present a slight welding conditiontherebetween it is desirable to provide a positive actuating means 88,particularly in the opening direction, to effect positive switch-openingmovement. To this end, there is provided a rotative kicker or actuator89, which is pivotally mounted on a pivot pin 90, and is positivelyengaged by an operating portion 460 (FIG. lb) of the driving crank arm66. When this occurs, the rotation of the actuator 89 will pick up thespring support 64 of the driven crank arm 65, as indicated in FIG. 7A ofthe drawings, thereby forcibly causing opening motion of the drivencrank arm 65. In similar manner, during the closing operation, theclosing motion of the operating portion 46b of the driving crank arm 46will engage a second pivotally mounted actuator 91, pivotally mounted ona pivot pin 92, and cause the tail portion 910 thereof to physicallyengage the spring supporting portion 64 of the driven crank arm 65 toeffect consequent closing movement thereof.

It is extremely desirable to provide a correct indication of the switchposition, that is whether the switch is open" or closed," inasmuch as anopen" indication of a switch, which in factjs closed, could present aserious hazard, and could result in a serious accident to operatingpersonnel.

It will be observed that if, due to excessive welding at the switchcontacts it is impossible to effect rotation of the actuators 89, 911,the line of action of the overcenter spring 63 will not pass over thecenterline 86 (FIG. It!) and the externally visible handle 34 willautomatically be retrieved to the closed position, thereby giving acorrect indication of the switch position.

With reference to FIG 5, it will be observed that the generally U-shapedplatelike frame support member 53 is secured, as by mounting bolts 93,to a generally U-shaped insulating lower frame support member 94 havingoppositely provided contact openings 95, 96 therein. The lower portionof the insulating frame member 9d has a bearing opening 97 therein toaccommodate the stub shaft 69, which, in turn, may be used to actuate asecond rectangular insulating shaft portion 68 for operating two furtherpairs of separable contacts 35, 75 and 76, 36. Reference may be had toFIG. 4 in this connection for a general diagrammatic showing of thearrangement of plural contact assemblies.

With reference to FIGS. 5-7 and 9, it willbe observed that there isprovided a pair of flexibly mounted spaced finger contacts 98, 99, eachof which comprises a stamped plate of good conducting material, such ascopper, and so configured as to be beveled at 98a, 99a (FIG. 9), andprovide alignment of the free end portions 75, 76 of the rotatable mainbridging contact member 71. A compression spring I00 is interposedbetween the outer ends of the contact fingers 98, 99 and seated onstamped projections 98c, 990. The contact fingers 98, 99 have a pair ofpositioning pins lill, I02 loosely extending through openings 98b, 99bprovided therein. A plate support member I04 (FIG. 6) is provided havingtabular portions 104a, l04b jutting outwardly therefrom to providesupporting portions for said pair of locating pins 101, I02. The upperend of the contact plate member I04 is secured, as by bolts I05, to thelower portion of the insulating frame support member 94. With theforegoing arrangement, it is obvious that the rotative action of themain bridging contact member 71 will be smoothly guided between thebeveled surfaces 980, 99a of the contact fingers 98, 99 to a propercontact seating engagement, as indicated by the dot-dash lines I06 ofFIG. 9.

From the foregoing it will be apparent that manual rotation of theeyelet handle 34, either by manual rotation thereof, or by switch-stickoperation by a serviceman, will effect rotation of the driving crank arm46 to thereby carry the line of action of the overcenter spring 63 to aposition where it will effect either snap-opening or snap-closingmovement of the lower driven, or follower crank arm 65. This will effectcorresponding opening or closing movement of the separable contactstructure; and an indicator plate I07, coupled with the rotatingindicator pointer 344, will indicate the open" or closed" circuitpositions of the switch 23.

As mentioned, further extensions of the operating shaft 68, includingadditional pairs of separable contacts as illustrated in FIG. 4, mayprovide a wide variety of circuit connections, as evidenced by FIGS. l5and I6 of the drawings.

FIGS. 17-24 SECOND SWITCH EMBODIMENT The novel load-break switch of thepresent invention may have another form of mechanism for more positivedetent control, as illustrated in FIGS. 20-24 of the drawings. Thisparticular embodiment of the invention may be used in a padmountedtransformer application of the type set forth in FIGS. 17-19 of thedrawings. For modern distribution applications, it is desirable in manyinstances to provide a pad-mounted application in which the distributiontransformer 6 is mounted upon a concrete pad I09, and is adaptable, in acentralized location, to provide power to a plurality of houses 110.Reference may be had to FIG. l7 in this connection.

The pad-mounted transformer 112, as illustrated in FIGS. I7 and I8,embodies a transformer tank 113, which is completely sealed andaccommodates the usual core-coil assembly and insulating oil. The top,bottom and walls are formed of onepiece heavy-gauge steel welded at thebottom seam, and the transformer compartment 113 is bolted to the cablecompartment 114; therefore convenient changeout to higher KVA ratings ispossible.

The cable compartment 114 provides a completely enclosed cabinet forterminating both the highand low-voltage cables so that no live partsare exposed. A free standing enclosure, this compartment can beinstalled, if desired, when the system is laid out, and the transformercompartment 113 added as distribution is needed. A lift-off door 115 iseasily removed for convenient access to both the highand low-voltagesections 117, 118. The low-voltage section 118 is separated from thehigh-voltage section 117 by a heavy insu- Iating mechanical barrier I20,and contains secondary terminals I5, l6 and I7 to feed the load circuits122-126 (FIG. l7), oil drain, etc.

As indicated in FIGS. 20 and 21, the load-break switch I28 is providedwith a manual eyelet handle 34 extending horizontally through thesidewall of the transformer tank compartment 113, thereby situating theswitch I28 beneath the level of the oil for more effectivearc-extinguishing action.

FIGS. 20 and 21 illustrate, respectively, in vertical section, and intop plan, a modified mechanism construction in which the spring supportmember 64' for the driven crank arm 65 is positively guided by a slotI29 provided in the lower frame support portion 85. It will be seen thatthe pin 64 on the lower spring arm 65 rides on a cam surface I30 cut outof the frame portion 85'. This permits more variety in detent actionthan is possible with a fixed bearing. An elongated slot I31 is providedin the lower frame member 85 to accommodate lateral movement of thestub-shaft portion 66' of the driven crank arm 65', as the springsupport pin 64' is moved along the cam slot I29. Again the overcenterspring action 63 insures a positive opening and closing movement of thedriven crank arm 65 by the provision of kickers" or actuators 89, 91,which are pivotally mounted in the top frame support portion 53', andfunction in a manner identical to that described hereinbefore.

The cam slot, illustrated in FIG. 21 of the drawings, shows a slotconfiguration 129 which is identical to the travel obtained by the crankdesign of FIG. 5 in controlling the pin 64 travel. FIG. 22 illustrates amodified type of cam slot I29, which is modified for greater detentaction at both ends of travel by being provided with end notches 130a,1301:. The corners 130a, I301) provide a detent action so that a greatertravel of the overcenter spring is required prior to an initial movementof the crank pin 64.

FIG. 23 is similar to the cam slot illustrated in FIG. 21; however, ithas a flattened portion of the center 134 for faster traverse of thedriven pin 64%. For still easier release of the driven pin 64, theconfiguration of the ends of the cam slot 129 could be as per the dottedlines M10 in FIG. 23. FIG. 24% is a modified type of cam slot, whichcombines the cam slot configurations of FIG. 22 and FIG. 23. i

From the foregoing it will be apparent that there are variousmodifications of the cam slots I29, which are possible for vari ouskinds of detent action desired. As will be obvious, the torque, which isnecessitated to start the motion of the driven crank arm 65', dependsupon the particular cam slot configuration 129 provided.

FIGS. 25-27 illustrate a modified type of contact structure, which hasbeen found to be far superior to the contact structure illustrated inFIGS. 7 of the drawings. In fact, the use of this contact design hasraised the level of successful close-in on a fault from 3,000 amperes toi0,000 amperes. A very important characteristic of the cooperatingcontact fingers is their stiffness characteristics, which has been foundsurprisingly to be of considerable importance. US. Pat. applicationfiled Jan. 22, 1968, Ser. No. 699,593, now US. Pat. 3,461,259 issuedAug. 12, 1969, to Merrill G. Leonard, Robert J. Manes-describes andclaims this variant contract structure.

In more detail, FIG. 25 illustrates a modified type of bolted lowersupport 150 having a central bearing opening 151 therethrough, whichaccommodates the contact holder stubshaft portion 152 so that thecooperating finger contacts 156 may make sliding engagement with thestationary contact blades l58, which are secured by bolts 159 to anoutwardly extending flange portion 150a of the molded lower insulatingsupport I50. The spring contact fingers I56 are comprised of a pluralityof laminations use, with the contacts ltil riveted to the outerextremity thereof and having a leaf spring l64, which bears upon theupper rivet portion 1610 of the contact l56, as illustrated more clearlyin FIG. 27 of the drawings. As mentioned hereinbefore, the stiffnesscharacteristic of the individual spring fingers is exceedingly importantas set out in the aforesaid patent application, and has led tosurprising results inasmuch as it has minimized any bouncing actionbetween the contact fingers 156 and the stationary contact blades l58.

The mechanism, which may be associated with the modified type of movablebridging contact structures I70, set forth in FIGS. 25-27, may be eitherof the type set forth in FIGS. 5- 7 of the drawings, or the mechanismmodification illustrated in FIGS. -24 of the drawings.

From the foregoing description of the load-break switch of the instantapplication, it will be observed that a highly effective quick make andquick-break action is secured during both the opening and closingmovements, with positive actuation being provided by the pivotallymounted actuator members 89, 91, which overcome any slight frictional orwelding resistance at the contacts. For excessive welding conditions,which render actuation of the actuators $9, 911 impossible, an automaticcorrect indication of switch position is provided.

Although there has been illustrated and described specific embodimentsof the invention, it is to be clearly understood that the same weremerely for the purpose of illustration, and that changes andmodifications may readily be made therein by those skilled in the artwithout departing from the spirit and scope of the invention.

I claim as my invention:

l. Switch means including a switch frame, a pair of actuators pivotallymounted on said switch frame, an actuating shaft having a rotatabledriving crank arm fixedly secured thereto, said rotatable crank armhaving a spring support at one end and a positive actuating portion atthe other extremity thereof for abutting engagement with said pair ofactuators, a driven crank arm having a spring support at one endthereof, an overcenter tension spring interconnecting the two springsupports for snap-opening and snap-closing action, separable contactsmechanically connected to said driven crank arm, each pivotal actuatorhaving an actuating end and a positive driving end, said actuating endbeing disposed in the path of movement of the positive actuating endportion of the rotatable driving crank arm, the positive driving end ofthe actuator positively driving the spring-supporting end of the drivencrank arm, for positively driving the driven crank arm should theseparable contacts become welded closed.

2. The combination of claim 1, wherein the line of action of theoverccnter tension spring does not pass over the centerline should thepivotal actuators fail to move due to excessive welding conditions atthe contacts, and thereby the handle being retrieved to its initialclosed position for correct switch indication position.

3. Switch means including a pair of spaced metallic plate portionshaving bearing openings therethrough in alignment, a pair of actuatorspivotally mounted on one metallic plate portion, an actuating shaftextending through the bearing opening of said one metallic plate portionand having a rotatable driving crank arm fixedly secured thereto, saidrotatable crank arm having a spring support at one end and a positiveactuating portion at the other extremity thereof for abutting engagementwith said pair of actuators, a driven crank arm having a spring supportat one end thereof, an overcenter tension spring interconnecting the twospring supports for snap-opening and snap-closing action, separablecontacts mechanically connected to said driven crank arm, each pivotalactuator having an actuating end and a positive driving end, saidactuating end being disposed in the path of movement of the positiveactuating portion of the rotatable driving crank arm, the positivedriving end of the actuator positively driving the spring-supporting endof the driven crank arm for positively driving the driven crank armshould the separable contacts become welded closed.

4. The combination according to claim 3, wherein a rotatable bridgingmember having two sets of cooperable flexible finger contacts isprovided.

5. In combination, a mounting member having an opening therethrough,switch-frame means including a bearing sleeve fixedly supported to themounting member, a sealing sleeve fixedly supported in said opening andsupporting a ring of elastomeric material, an actuating switch memberrotatably mounted with a relatively tight fit in said bearing sleeve andwith a relatively loose fit in said sealing sleeve, and shoulder meanson said bearing sleeve telescoping within a shoulder portion of thesealing sleeve for providing concentricity of the two sleeves.

6. The combination according to claim 1 wherein a cam slot guides themotion of the driven rotatable crank arm.

7. The combination according to claim 6, wherein detent notches areprovided at the ends of said cam slot.

8. The combination according to claim 6, wherein the cam slot is widenedat the intermediate portion thereof to thereby reduce the detent action.

9. The combination according to claim 1, wherein a rotatable bridgingmember having two sets of cooperable flexible finger contacts isprovided.

10. The combination according to claim 3, wherein the other metallicplate portion is provided with a cam slot which guides the motion of thedriven rotatable crank arm.

ill. The combination according to claim 10, wherein detent notches areprovided at the ends of said cam slot.

12. The combination according to claim ll, wherein the cam slot iswidened at the intermediate portion thereof to thereby reduce the detentaction.

13. The combination according to claim 5, wherein the mounting member isa transformer casing, and the actuating switch member is a rotatableoperating shaft extending externally of the transformer casing.

M. The combination according to claim 5, wherein the switch-frame meansis a generally rectangularly shaped member.

15. The combination according to claim 1, wherein spaced stops formed onthe frame limit the degree of rotation of the driving crank arm.

16. The switch means of claim 3, wherein the line of action of theovercenter tension spring does not pass over the centerline should thepivotal actuator fail to move due to excessive welding conditions at thecontacts, and thereby the handle being retrieved to its initial closed"position for correct switch indication position.

17. Switch means including a switch frame, at least one actuatorpivotally mounted on said switch frame, an actuating shaft having arotatable driving crank arm fixedly secured thereto, said rotatablecrank arm having a spring support at one end and a positive actuatingportion adjacent the other extremity thereof for abutting engagementwith said one actuator, a driven crank arm having a spring support atone end thereof, an overcenter tension spring interconnecting the twospring supports for snap-opening and snap-closing action, separablecontacts mechanically connected to said driven crank arm, said onepivotal actuator having an actuating end 10 and a positive driving end,said actuating end being disposed in the path of movement of thepositive actuating portion of the-rotatable driving crank arm, thepositive driving end of the actuator positively driving thespring-supporting end of the driven crank arm should the separablecontacts become welded closed.

18. The combination according to claim 3, wherein spaced stops areformed on the switch frame to limit the degree of rotation of thedriving crank arm.

19. The combination of claim 17, wherein the line of action of theovercenter tension spring does not pass over the centerline should thepivotal actuator fail to move due to excessive welding conditions at thecontacts, and thereby the handle being retrieved to its initial closedposition for correct switch indication position.

1. Switch means including a switch frame, a pair of actuators pivotallymounted on said switch frame, an actuating shaft having a rotatabledriving crank arm fixedly secured thereto, said rotatable crank armhaving a spring support at one end and a positive actuating portion atthe other extremity thereof for abutting engagement with said pair ofactuators, a driven crank arm having a spring support at one endthereof, an overcenter tension spring interconnecting the two springsupports for snap-opening and snap-closing action, separable contactsmechanically connected to said driven crank arm, each pivotal actuatorhaving an actuating end and a positive driving end, said actuating endbeing disposed in the path of movement of the positive actuating endportion of the rotatable driving crank arm, the positive driving end ofthe actuator positively driving the spring-supporting end of the drivencrank arm, for positively driving the driven crank arm should theseparable contacts become welded closed.
 2. The combination of claim 1,wherein the line of action of the overcenter tension spring does notpass over the centerline should the pivotal actuators fail to move dueto excessive welding conditions at the contacts, and thereby the handlebeing retrieved to its initial ''''closed'''' position for correctswitch indication position.
 3. Switch means including a pair of spacedmetallic plate portions having bearing openings therethrough inalignment, a pair of actuators pivotally mounted on one metallic plateportion, an actuating shaft extending through the bearing opening ofsaid one metallic plate portion and having a rotatable driving crank armfixedly secured thereto, said rotatable crank arm having a springsupport at one end and a positive actuating portion at the otherextremity thereof for abutting engagement with said pair of actuators, adriven crank arm having a spring support at one end Thereof, anovercenter tension spring interconnecting the two spring supports forsnap-opening and snap-closing action, separable contacts mechanicallyconnected to said driven crank arm, each pivotal actuator having anactuating end and a positive driving end, said actuating end beingdisposed in the path of movement of the positive actuating portion ofthe rotatable driving crank arm, the positive driving end of theactuator positively driving the spring-supporting end of the drivencrank arm for positively driving the driven crank arm should theseparable contacts become welded closed.
 4. The combination according toclaim 3, wherein a rotatable bridging member having two sets ofcooperable flexible finger contacts is provided.
 5. In combination, amounting member having an opening therethrough, switch-frame meansincluding a bearing sleeve fixedly supported to the mounting member, asealing sleeve fixedly supported in said opening and supporting a ringof elastomeric material, an actuating switch member rotatably mountedwith a relatively tight fit in said bearing sleeve and with a relativelyloose fit in said sealing sleeve, and shoulder means on said bearingsleeve telescoping within a shoulder portion of the sealing sleeve forproviding concentricity of the two sleeves.
 6. The combination accordingto claim l wherein a cam slot guides the motion of the driven rotatablecrank arm.
 7. The combination according to claim 6, wherein detentnotches are provided at the ends of said cam slot.
 8. The combinationaccording to claim 6, wherein the cam slot is widened at theintermediate portion thereof to thereby reduce the detent action.
 9. Thecombination according to claim l, wherein a rotatable bridging memberhaving two sets of cooperable flexible finger contacts is provided. 10.The combination according to claim 3, wherein the other metallic plateportion is provided with a cam slot which guides the motion of thedriven rotatable crank arm.
 11. The combination according to claim l0,wherein detent notches are provided at the ends of said cam slot. 12.The combination according to claim ll, wherein the cam slot is widenedat the intermediate portion thereof to thereby reduce the detent action.13. The combination according to claim 5, wherein the mounting member isa transformer casing, and the actuating switch member is a rotatableoperating shaft extending externally of the transformer casing.
 14. Thecombination according to claim 5, wherein the switch-frame means is agenerally rectangularly shaped member.
 15. The combination according toclaim l, wherein spaced stops formed on the frame limit the degree ofrotation of the driving crank arm.
 16. The switch means of claim 3,wherein the line of action of the overcenter tension spring does notpass over the centerline should the pivotal actuator fail to move due toexcessive welding conditions at the contacts, and thereby the handlebeing retrieved to its initial ''''closed'''' position for correctswitch indication position.
 17. Switch means including a switch frame,at least one actuator pivotally mounted on said switch frame, anactuating shaft having a rotatable driving crank arm fixedly securedthereto, said rotatable crank arm having a spring support at one end anda positive actuating portion adjacent the other extremity thereof forabutting engagement with said one actuator, a driven crank arm having aspring support at one end thereof, an overcenter tension springinterconnecting the two spring supports for snap-opening andsnap-closing action, separable contacts mechanically connected to saiddriven crank arm, said one pivotal actuator having an actuating end anda positive driving end, said actuating end being disposed in the path ofmovement of the positive actuating portion of the rotatable drivingcrank arm, the positive driving end of the actuator positively drivingthe spring-supporting end of the driven crank arm should the separablecontacts become welded closed.
 18. The combination according to claim 3,wherein spaced stops are formed on the switch frame to limit the degreeof rotation of the driving crank arm.
 19. The combination of claim l7,wherein the line of action of the overcenter tension spring does notpass over the centerline should the pivotal actuator fail to move due toexcessive welding conditions at the contacts, and thereby the handlebeing retrieved to its initial ''''closed'''' position for correctswitch indication position.